Recently, there has been a growing urgency to develop lasting therapies for several pathologies that have withstood traditional antibiotics. This has given rise to, among others, a greater need to develop more effective antibiotics and anti-neoplastic agents. Coincidentally, this comes at a time when a mounting evidence is accumulating indicating the widespread distribution in Streptomycetes of silent genes for secondary metabolites, and the potential to harness such genes for the production of novel antibiotics. One such group of silent genes consists of those for phenoxazinone synthase (PHS), a key enzyme in the pathway of actinomycin D biosynthesis in Streptomyces antibiotics of silent. This applicant realizes the limited clinical use of actinomycin D as an antineoplastic agent, and proposes to examine the silent homologs of the PHS gene in Streptomycetes, as potential candidates for a genetic modification of the actinomycin biosynthetic pathway to produce clinically more use&l analogs of this antibiotic. The specific aims of the proposed research will therefore include: (i) cloning and characterizing the silent gene(s) for the enzyme phenoxazinone synthase (PHS) from Streptomyces coelicolor, and Streptomyces glaucasence; (ii) elucidating the mechanism of cryptification, and activation, of the gene(s); (iii) isolating the entire cluster of genes for the putative pathway; and (iv) exploring, through molecular intervention, the potential role of these silent alleles in the production of actinomycin or other antineoplastic agents. It is anticipated that the proposed experiments will yield a significant amount of information which will be useful in continued examination of members of this bacterial genus for silent pathways for the synthesis of novel antibiotics. This project will also provide a much-needed opportunity for the training of undergraduate students at the applicant institution, in the area of molecular biology and microbial genetics.